Use serial interface on Tang Nano FPGA board

Hello together

This is Gerhard from Austria.

I am using the TANG NANO FPGA Board. It is a cool board!

I saw that two pins FPGA_RX and FPGA_TX are connected to the CH552T.

My Question: Can the FPGA_RX and FPGA_TX-pin also be used for RS232 user applications?

I tried to define RxD-Pin as digital input for my serial receiver verilog code but
running “Place and Route” in GoWin creates an error.

Thank you for your help

Gerhard